Strength training strategies to improve endurance performance

Successful performance in endurance events including middle to long distance running, cycling, cross country skiing and biathlon is dependent on numerous physical qualities. These include, but are not limited to; aerobic capacity and power (V̇O_2max), fatigue resistance, high intensity work capacity and power (anaerobic capacity), lactate threshold, speed maintenance and the relative energy cost of the running, cycling or skiing (economy/efficiency). These qualities can be improved by “traditional” endurance training strategies such as continuous, high intensity interval, sprint interval and threshold training.

Generally, amongst lesser trained individuals the primary predictor of aerobic performance is V̇O_2max. However, in those who are highly trained or elite athlete populations, it is likely that that economy, lactate threshold and velocity at lactate threshold are more important predictors of performance. In brief, economy refers to the oxygen consumption required at a given intensity and distance. Taking body mass into consideration, athletes with good economy use less energy and therefore less oxygen than those with poor economy at the same intensity and/or workload¹.

Lactate threshold broadly refers to the intensity at which blood lactate concentrations begin to increase quickly. As such, athletes and coaches have sought out new training methods to achieve improvements in economy, lactate threshold and endurance performance.

Since the early 2000’s a growing body of scientific research has indicated that the addition of strength training strategies to an endurance athletes training programme, or “concurrent training” can be an effective means of improving economy, lactate threshold and endurance performance. Based on this research and advances in sport science and strength and conditioning practice it is now more common for endurance athletes to engage in strength training ². Previously, a potential concern endurance athletes and coaches may have had is that strength training may result in increases in muscle mass (hypertrophy) and result in the athlete becoming too heavy. This need not be a concern, as research has demonstrated that improvements in strength and endurance performance can be achieved with minimal or no increases in body and muscle mass³, if strength training is prescribed appropriately and targets neuromuscular, rather than hypertrophic adaptations.

Generally, when endurance athletes first started to adopt strength training strategies, the programmes involved high repetition (reps) schemes with low loads, or “strength endurance training”. It was thought that this would best replicate the demands of the sport(s). Whilst this appears logical, research has indicated that this is not the most effective means of improving endurance performance via strength training. It appears that “heavy strength training”, which refers to training aiming to increase or maintain a muscle groups maximal force production capabilities and “explosive strength training”, referring to training with the emphasis placed on completing the movement at high velocities may be more effective. Heavy strength training typically involves loads which allow between 2 to 5 reps in well trained individuals and 1 to 10 reps in lesser trained individuals, to be performed per set, whereas explosive strength training involves loads between 0-60% of the athlete’s 1 repetition maximum (1 RM).

Running

A number of studies have reported running economy to be improved following concurrent heavy strength and endurance training^4–6. Furthermore, concurrent explosive strength and aerobic training has also been observed to result in improved economy in runners⁷.

The durations of the training programmes in the aforementioned studies ranged from 6 – 14 weeks, demonstrating that improvements in economy via concurrent training strategies can be achieved over a relatively short period, this however is of course dependent on programme variables including; training volumes, exercise selection and load in the respective programmes.

It appears relatively conclusive that concurrent training is an effective means of improving running economy. However, concurrent training’s influence on lactate threshold appears less conclusive. Some studies report no additional benefit of adding strength training to a runners programme^7,8, whereas others report substantial improvements in speed at lactate threshold⁵.

Similar to economy, the influence of concurrent training on lactate threshold is likely dependent on the programme variables employed. It is also worth noting that no studies have reported any negative impact of concurrent training strategies on lactate threshold in runners.  

Perhaps most importantly, substantial amounts of research have indicated concurrent training strategies are superior to endurance training alone for improving time trial and running performance in trained runners. This augmented performance is likely due to improvements in running economy and potentially speed at lactate threshold.

Cycling

Whilst the majority of studies in running report positive effects of concurrent training on economy, research conducted in cyclists has reported little change in cycling economy following combined heavy and explosive strength training in highly trained cyclists^9,10. Separate work has however reported that 8 weeks of adding heavy strength training to cycling training improved economy, although the cyclists were a slightly lower performance level¹¹. There is comparatively little information on the influence of concurrent training on lactate threshold in cyclists. However, concurrent heavy strength and endurance training can improve maximum power output during cycling (W_max) and time to exhaustion at W_max. Interestingly, this effect was only observed following heavy and not explosive strength training¹¹, which may indicate heavy strength training is more beneficial for cyclists. Similar to running, whilst not all performance variables mentioned here were improved by concurrent training, there is no evidence that any of the aforementioned variables are negatively influenced by heavy nor explosive strength training.

In addition to positively influencing endurance performance characteristics, the primary adaptation to strength training is, of course, increased muscular strength and ability to produce high levels of force. There are numerous situations in cycling in which increased lower body maximal strength would be beneficial, such as; gaining an advantageous position at the start of the race, breaking away from the peloton, or a final sprint finish. Furthermore, concurrent training involving heavy strength training has been reported to result in 7% greater power output during a final 5-min maximal sprint than endurance training alone¹⁰.

Cross Country Skiing & Biathlon

When compared with running and cycling there is surprisingly little research into strength training strategies in cross country skiers. However, the research which has investigated the addition of strength training to cross country ski training has reported a positive effect of strength training on skiing performance. In adult competitive skiers, 12 weeks of upper and lower body heavy strength training including 3 sets of 5 – 10 RM conducted alongside high volume ski training resulted in improved V̇O_2max during roller skiing and double poling performance, compared with skiers who performed only ski training³. Furthermore, the improved performance following strength training was not coupled with increases in muscle mass. This indicates it is possible to improve cross country ski performance without additional muscle mass via strength training. Additional research reported well trained male skiers who performed strength training achieved greater improvements in submaximal double poling and rolling skiing time to exhaustion than those who performed equal volumes of ski training alone¹². This is likely due to strength training resulting in in greater rate of force development (RFD) which can be transferred to the poles for propulsion.

In contrast to the research in male skiers, one study in junior female skiers reported no beneficial effect of upper body strength training on double poling performance, despite the athletes becoming stronger. This may be due to the fact that junior athletes did not have adequate technique to transfer their increased strength to technical performance¹³.

Whilst there is little specific research on strength training strategies in biathlon, the aforementioned research in cross country skiers indicates that strength training can have beneficial effects on upper body performance (double poling). As such, it is not unreasonable to suggest that strength training may improve rifle carriage and double poling abilities in biathletes.

Potential mechanisms for improvements in endurance performance

Whilst we cannot be 100% certain of the exact physiological changes that contribute to improved endurance performance following concurrent training, some potential mechanisms have been proposed. It is possible that strength training enables athletes to recruit more fast rather than slow twitch muscle fibres during certain points in their performance. This would enable them to improve RFD and result in less time being taken to reach the required force to complete each movement cycle (in running a stride or cycling a revolution). In addition, it is possible that increased RFD may result in increased blood flow to the working muscle, resulting in improved recovery¹⁴.

Perhaps most relevant to running, strength training (particularly explosive strength training) can improve tendon stiffness. Broadly, this enables the athletes to better utilise elastic energy. If the athlete can better utilise elastic energy, the remaining energy requirements for running would be lower, which is directly related to running economy.

Practical recommendations

Whilst it is apparent that the addition of strength training to endurance training programmes can have positive effects on economy and endurance performance in recreational and highly trained athletes, certain considerations should be made before implementing or undertaking any strength training strategies.

The first consideration and priority, is of course, athlete safety. Prior to any heavy or explosive strength training coaches and athletes must ensure that the individual undertaking strength training has sufficient movement competency to perform the exercises prescribed. If the athlete is unable to properly perform simple movement patterns such as; pushing, pulling, hinging at the hip, squatting, rotating and bracing the trunk it is possible that any exercise performed will be done so with incorrect technique and may result in injury if the load is too great. As such, movement competency should be developed before any strength training with heavy external loads is conducted. This consideration is particularly important in youth athletes.

In terms of exercise selection, it is imperative that the strength training exercises involve similar muscle groups to those used in the sport. It is also important that the programme includes strength training exercises which are similar (not necessarily identical) to the sport specific movements. For example, squat and/or leg press which involve extension at the hip and knee joint for cycling. For running or skiing specifically, clean derivatives or ballistic exercises such as jump squats which involve triple extension at the ankle, knee and hip are likely beneficial.

To achieve improvements in economy and endurance performance research indicates that 2 strength training sessions per week are recommended. This of course is subject to change depending on the competitive season and periodization strategies. If 2 strength type sessions per week can be performed during the off season, it is likely that 1 high quality session per week is sufficient to maintain any improvements in strength and economy during the competitive season. It is also recommended that training programmes involve a combination of heavy and explosive strength training concurrent to endurance training. Similar to training frequency, when these types of strength training are implemented should be dictated by the competitive season with more heavy strength training being performed in the off season and more explosive training close to and potentially during the competitive season.

To conclude, concurrent strength and endurance training can be an effective means of improving economy and performance in middle to long distance runners, cyclists, cross country skiers, and biathletes, as well as recreationally trained individuals. Coaches and athletes should make certain considerations around safety, exercise selection, training frequency, periodization, and the type of strength training performed to maximise the benefits of strength training for endurance performance.

References

1. Saunders PU, Pyne DB, Telford RD, Hawley JA. Factors affecting running economy in trained distance runners. Sports Med. 2004;34(7):465-485. doi:10.2165/00007256-200434070-00005
2. Blagrove RC, Brown N, Howatson G, Hayes PR. Strength and Conditioning Habits of Competitive Distance Runners. J strength Cond Res. 2017;33(8):2287-2297. doi:10.1519/JSC.0000000000002261
3. Losnegard T, Mikkelsen K, Rønnestad BR, Hallén J, Rud B, Raastad T. The effect of heavy strength training on muscle mass and physical performance in elite cross country skiers. Scand J Med Sci Sport. 2011;21(3):389-401. doi:10.1111/j.1600-0838.2009.01074.x
4. Taipale RS, Mikkola J, Nummela A, et al. Strength training in endurance runners. Int J Sports Med. 2010;31(7):468-476. doi:10.1055/s-0029-1243639
5. Guglielmo LGA, Greco CC, Denadai BS. Effects of strength training on running economy. Int J Sports Med. 2009;30(1):27-32. doi:10.1055/s-2008-1038792
6. Millet GP, Jaouen B, Borrani F, Candau R. Effects of concurrent endurance and strength training on running economy and .VO(2) kinetics. Med Sci Sports Exerc. 2002;34(8):1351-1359. doi:10.1097/00005768-200208000-00018
7. Paavolainen L, Häkkinen K, Hämäläinen I, Nummela A, Rusko H. Explosive-strength training improves 5-km running time by improving running economy and muscle power. J Appl Physiol. 1999;86(5):1527-1533. doi:10.1097/00003246-198707000-00023
8. Mikkola J, Rusko H, Nummela A, Pollari T, Häkkinen K. Concurrent endurance and explosive type strength training improves neuromuscular and anaerobic characteristics in young distance runners. Int J Sports Med. 2007;28(7):602-611. doi:10.1055/s-2007-964849
9. Aagaard P, Andersen JL, Bennekou M, et al. Effects of resistance training on endurance capacity and muscle fiber composition in young top-level cyclists. Scand J Med Sci Sports. 2011;21(6):e298-307. doi:10.1111/j.1600-0838.2010.01283.x
10. Rønnestad BR, Hansen EA, Raastad T. Strength training improves 5-min all-out performance following 185 min of cycling. Scand J Med Sci Sports. 2011;21(2):250-259. doi:10.1111/j.1600-0838.2009.01035.x
11. Sunde A, Støren O, Bjerkaas M, Larsen MH, Hoff J, Helgerud J. Maximal strength training improves cycling economy in competitive cyclists. J strength Cond Res. 2010;24(8):2157-2165. doi:10.1519/JSC.0b013e3181aeb16a
12. Øfsteng S, Sandbakk, van Beekvelt M, et al. Strength training improves double-poling performance after prolonged submaximal exercise in cross-country skiers. Scand J Med Sci Sport. 2018;28(3):893-904. doi:10.1111/sms.12990
13. Skattebo, Hallén J, Rønnestad BR, Losnegard T. Upper body heavy strength training does not affect performance in junior female cross-country skiers. Scand J Med Sci Sports. 2016;26(9):1007-1016. doi:10.1111/sms.12517
14. Stöggl T, Björklund G, Holmberg H-C. Biomechanical determinants of oxygen extraction during cross-country skiing. Scand J Med Sci Sports. 2013;23(1):e9-20. doi:10.1111/sms.12004

Further reading

Berryman N, Mujika I, Arvisais D, Roubeix M, Binet C, Bosquet L. Strength Training for Middle- and Long-Distance Performance: A Meta-Analysis. Int J Sports Physiol Perform. May 2017:1-27. doi:10.1123/ijspp.2017-0032

Rønnestad BR, Mujika I. Optimizing strength training for running and cycling endurance performance: A review. Scand J Med Sci Sport. 2014;24(4):603-612. doi:10.1111/sms.12104